The goal of this project is the development of a cyclic-AMP(cAMP)- stimulated "sweat rate" test that will discriminate between fully functional, partially functional, and non-functional forms of the Cystic Fibrosis Transmembrane Conductance Regulator(CFTR). Sweat production can be stimulated by both cholinergic & adrenergic agonists. Collection of cholinergic stimulated sweat & the subsequent measurement of sweat cholride concentration is the basis of a standard diagnostic test for cystic fibrosis (CF), the pilocarpine iontophoresis sweat test. Stimulation of sweat production with pilocarpine leads to initial production of an isotonic secretion in the sweat gland. In non-CF patients, as the secretion traverses the sweat duct, chloride is reabsorbed leading to low concentrations of chloride in sweat as it appears on the skin. This chloride resorption is dependent on the presence of functional CFTR. In CF patients, who lack functional CFTR, the sweat chloride concentration remains high, & distinguishes most, but not all, CF from non-CF patients. However, this technique does not distinguish heterozygote carriers of CFTR mutations from non-carriers, nor does the sweat chloride concentration correlate with disease severity.